1. Field of the Invention
The present invention relates generally to apparatus for testing jet engines. In particular, the present invention relates to an annular after reactor (AAR) positioned in the exhaust of a jet engine under static test to remove particulate matter and other environmentally unsafe compounds from the exhaust of the jet engine.
2. Description of the Prior Art
The National Ambient Air Quality Standards established by the Clean Air Act requires the removal of fine particle concentrations from the atmosphere in an effort to decrease lung disease and related illnesses as well as mortality rates in urban areas. Currently, the standards have a criteria of PM10 (particles smaller than 10 microns in diameter, however, a standard for PM2.5 is in the process of being imposed. In addition, the Clean Air Act provides for the promulgation of national emission standards for engine test facilities including jet engine test cells.
The emissions of particulate matter, nitrogen oxides (NO.sub.x), carbon monoxide and unburned hydrocarbons from the engine exhaust from a jet engine under test has been a concern of the military for two decades, however a cost effective approach for reduction of these environmentally harmful emissions remains to be identified.
Further, the problems that must be addressed to control these emissions are considerable, including the following: (1) the pollutant must be removed from large quantities of engine exhaust as well the augmentation air that accompanies and mixes with the exhaust; (2) the exhaust gases move at velocities of up to 3000 ft/sec and have temperatures of up to 3000 degrees Fahrenheit; (3) the operational conditions of jet engine test cells change frequently so that steady state operation is difficult to achieve; (4) proper test conditions require that only a limited back pressure be developed in the test cell augmentation tube; and (5) the cost for treatment of an exhaust stream from a jet engine is proportional to the total exhaust gas flow and inversely proportional to the pressure drop permitted.
One prior art approach provided for the use of water sprays to remove particulate matter from the jet engine exhaust stream. However, the approach led to the creation of acidic fallout near the jet engine test cell. In addition, the use of water sprays to remove PM2.5 particulates (i.e., particulates of a size less than 2.5 microns in diameter) is generally ineffective since particulates of the order of 2.0 microns tend to follow streamlines around water droplets rather than be collected on them by impaction.
Other prior art approaches such as the use of a filter bed to remove particulate matter from jet engine exhausts have also been shown to be very ineffective and costly.
Accordingly, there is a need for a relatively simple, cost effective and highly efficient apparatus for the removal of particulate matter and other environmentally harmful compound from the exhaust of a jet engine under test.